Superdurable photo plates for ink printing



Io Drawing.

Patented Aug. 30, 1927.

UNITED STATES ALBERT :r. rmcxnnx, or NEW YonxQN. x.

SUIEEBDUBABLE PHOTO PLATES FOR INK PBINTmG.

This invention relates to the art of producing photo-plates of the typeemployedin thejofi'set process of ink-printing. The object of theinvention is primarily to increase the life of such a plate from acapability of printing only a few thousand co ies up to several tens ofthousand copies. n fact, I have increased the life of such a plate tosuch an extent that a quarter of a million copies have been reproducedfrom it without the plate becoming defective.

In general, it is an object of my invention to improve both aphoto-plate of the type employed for offset printing and to cheapen andimprove the process by which such plates are fabricated.

In the preferred practice of my invention,

' I started with a sheet of sheet metal, such 'of the plate in dryweather with any suitable water solution of egg albumen and a lightsensitive salt of a character capable of hardening the albumen uponexposure to light. I prefer to employ thefollowing ingredients by weightin the formation of this solution: 3 ozs. of ammonium dichromate; 3 ozs.dry egg albumen; .and 32 ozs. of water. I

= This solution must be used fresh, that is,-

before any decomposition of the egg albumen has taken place, and issuitable for use in dry weather.

For damp weather, toeach 10 ozs. of the above solution, I prefer to addfrom one half to one ounce of grain alcohol. The alcohol renders thissolution suitable for use in damp weather and insures an adherent toughalbuminous film on the plate.

Fifth, I dry the "film coated plate in a whirler which throws offall'excess solution and by maintaining a dry atmosphere over.

the plate dries the surface into a substantially dry film-coatedsurface.

S'xth, he film coated surface of the plate is' exposed to an imagecarrying beam or Application filed December 10, 1926. Serial no.154,039.

flood of light as by causing li ht to shine through an ordinary photorap ic negative of the desired image in light and shade. This step in myprocess is similar to the printing of any sensitized surface through anegative. I prefer, however, to employ a large metal plate many timeslarger than the images to be made upon its surface and to repeat them byuniformly timed exposures first on one spot and then on another spot,until the surface of the metal plate is covered with the desired numberof light impressions. The exposure of each light impression should takefrom about one and a half to two minutes each. Speaking generally, thisexposure should be of the normal and proper amount to give the desiredclarity of image. It is not at' this step that durability is imparted tothe film in accordance with my invention.

Seventh, I rub over the film coated surface after it has beenexposed tothe image producing light with an oily developing blacking ink,preferably of the type known in the trade as Directof although any inkysubstance comprising crayon black mixed with castor oil and a littleturpentine is suitable. The adherence or embedding of this black inkupon the surface of the film varies according to the variation in thelightformed images upon the albuminous film. But this does not appear tothe sense of sight, until after the next step.

Eighth, after drying the ink surface I submerge it in water and whilecarefully keeping the entire surface of the plate under watergently rubthe inked albuminous surace preferably with a soft sponge of cottondberlg The images then appear in light and Ninth, I take the plate outof the water and dry it.

Tenth, I expose thev entire film-coated surface of the plate upon whichthe images appear in varying degrees of the black ink as nearly aspossible to surface normal rays from a powerful actinic'light for fromfive to ten minutes. I have successfully used carbon are light, two arcsabout six inches apart in the flaring hood with the .arc separatedsomething like four or five feet from the center of a single plate,approximatelly about 3 by 4 feet in surface dimensions. t is tobeunderstood that this expeosure to the intense actinic light is not tolimited to are light, as an; suitable source of actinic light iscontemplated, such as sun-light. It should also be understood that thisexposure to light at this stage of my process is of extreme importance.I found further that without light treatment at this time. thedurability of the finished photo plate is less than ten percent of whatit is when so treated. It is probable that by this procedure 'I-eff'ectthe light hardening of the entire film of albuminous matter withoutchanging any of the detail already produced on the film. In other words,I imprison all the refinements of the photographic art practiced underfavorable conditions by employing a separate uniform exposure to lighttoaccomplish the hardening after I have first used only the most favorableamount of ex posure to produce the image.

Eleventh, I coat the entire surface of the plate with a thin watersolution of gum arabic and dry the surface.

Twelfth, the gum arabic coated surface of the plate is rubbed off withcrayon black and washed off with water clean and then is dried.

Thirteenth, I dust off the surface of the plate with a black powder,preferably asphaltum powder.

Fourteenth, the functioning surface of the plate is edged. In accordancewith my process, the edging may be accomplished in any of the usualWays, for example,

with an ammonia edge, or with a. chromic acid edge.

Fifteenth, after edging the surface of the plate is washed off cleanwith distilled water.

Sixteenth, the entire'surface is rubbed off with a thin solution of gumarabic and dried.

Seventeenth, the surface of the late is carefully washed over withturpentine and subjected to light abrasion as with a cotton fibersponge. This turpentine washing removes all visible black.

Eighteenth, the surface'of the plate is then rubbed over with liquidasphaltum which adheres to the film foundation in image producingproportions. The asphaltum does not adhere to the surface, except whereand in the amount required to produce the dark parts of the desiredimage. The applied liquid asphaltum is allowed to dry and it is thisasphaltum surface which constitutes the ink printed surface of thefinished photo plate; and as I have previously set forth by this processproduce a photo plate capable of reproducing in an offset printingmachine a quarter of a million impressions, whereas heretofore I havefound that photo-plates would reproduce only at best a few-thousandimpressions.

In its broader aspects, my process is equally applicable to theproduction of albuminous printing films upon stone lates, which shouldbe treated in substantial y the same way as described above inconnection with the grained surface in'a sheet metal plate. The type ofstones to which I am re- I 1. A photoplate of the type employed in Yoffset printing comprising a surface-grained flexible sheet-metal plate;an image imparting printing film of light-hardened albuminous matterwhich is over-exposed but with highlights, whereby the finished plate isof markedly increased durability for the production of offsetimpressions.

2. A photoplate of the type employed in offset printing comprising aplate; an image imparting printing film of light hardened albuminousmatter which is over-exposed but with highlights, whereby the finishedplate is of markedly increased durability for the production of offsetimpressions.

3. A form of plate of the type employed in offset printing comprisingmeans providing a grained surface; an image imparting printing film ofover-exposed lighthardened albuminous matter with its printing surfacecorresponding as to its image qualities with that of a -film normallyexposed to image strained light but of increased durability in thereproduction of offset impressions.

4. The process of forming photo-plates of the type employed in offsetprinting comprising coating the grain surface of a sheet metal platewith a water solution of albumen and a light sensitive salt of the typecapable of hardening albumen on exposure to light; exposing the saidcoated surface to image strained light; spreading an ink mixture ofpulvurent black substance and oil over said surface; subjecting saidinked surface to the solvent action of water and gentle abrasion; thenexposing said entire surface for some five to ten minutes to the directaction of strong actinic light; and subsequently edging and finishingsaid plate in accordance with any usual procedure here allowable wherebybecause of the said exposure of the: incomplete printing surface tostrong act-inic light between the time it' is edged and the time it isexposed to image strained light,

a toughening of the image carrying film is effected.

5. The toughening of offset printable films on photo-plates comprisingexposing a light sensitive albuminous film to i the desired image inlight and shade; coating the said film with an oily black ink;subjecting said film to the solvent action of Water and gentle surfacerubbing to bring out said image into visibility from said ink; thenexposing said entire surface to intense actinic light for a considerableperiod of time, such as ing a light printed image on a light sensi- 10tive albuminous film with a black oily ink and then subjecting said filmto relatively long exposure to strong actinic light shining directlyupon said ink developed image.

In witness whereof, I have signed my 15 name to this specification, this4th day of September, 1926.

. ALBERT J. PINCKNEY.

